At present, a liquid crystal display (LCD), an electroluminescence (EL) display, an electronic paper and other display devices are well known. These display devices have a thin film transistor (TFT) to turn on or turn off a pixel. As shown in FIG. 1, the thin film transistor mainly comprises an active layer 1, a gate electrode 2, a source electrode 3 and a drain electrode 4 provided on a base substrate 0; a gate insulation layer 5 is provided between the active layer 1 and the gate electrode 2, the source electrode 3 and drain electrode 4 are arranged in a same layer, an insulation layer 6 is provided between the source electrode 3 and the drain electrode 4 and the gate electrode 2, and the source electrode 3 and the drain electrode 4 are respectively electrically connected with the active layer 2. With respect to the thin film transistor shown in FIG. 1, in order to form a low-doped region P, the active layer 1 needs to be processed with H2, NH3, He, or other plasma. The low-doped region P is provided close to a channel region in the active layer 1, to prevent a thermal electron degradation effect.
As described above, during the plasma process for forming the low-doped region P, the active layer 1 is processed with a gas having a high hydrogen content such as H2, NH3 and the like; in this case, it is possible that the active layer 1 (particularly, in the case that the active layer is formed of a semiconductor oxide) becomes conductive due to an action of hydrogen, so as to destroy semiconductor characteristics of the active layer 1.